Physical and chemical properties of the acid protease from <i>Onopordum acanthium</i>: Comparison between electrophoresis and HPLC of degradation casein profiles

Abstract

A protease was extracted by grinding, precipitation and gel filtration from Onopordum acanthium flowers. The physicochemical study of the enzyme showed an optimum pH of 4, a temperature of 40°C and kinetic parameters of 12.25 mM^-1 for K_M and 1329.6 UmL^-1 for V_max. The inhibition by pepstatin indicated that it is an aspartyl-protease (APs). Zymogram showed that the protease has a monomeric structure and a molecular mass (MM) of 45 kDa. The hydrolysis of α, β and Κ- and whole casein by the protease was evaluated using electrophoresis and HPLC; the profiles showed many similarities between the vegetal protease action and that of industrial chymosin. So, the properties of the protease studied and the quality of its action showed its effectiveness and relevance of its use as a milk clotting enzyme which leads to a better use of extract of flowers O. acanthium as a locally substitute for rennet.

Keywords: Aspartic protease, Onopordum acanthium, purification, characterization, casein hydrolysis